1921] MEIER—ROOT TIP I17 
In 1914 Harpy (9) published a short note on the migration under 
influence of the direct current of the contents of cells of the onion 
root tip. His methods and results were briefly as follows. The 
roots were placed horizontally between non-polarizable electrodes, 
the final lead to the tissue being some of the fluid in which the roots 
had been growing. As to the density of current used and the time 
of exposure, the author states: ‘‘A field of 5-20 volts per cm. was 
established for from 1 to 10 minutes, when the root was instantly 
fixed in acetic-absolute. Strength of field to which the living 
matter was actually exposed cannot be calculated.”’ The effect 
produced was uniform, and varied only with intensity of current 
-and time of exposure. The nucleus was usually slightly drawn out 
from a sphere to an ellipsoid, with the long axis parallel to the 
direction of the current flow. The nucleus maintained its position 
in the middle of the cell. The cytoplasm collected usually at the 
end of the cell toward the cathode, although frequently condensed 
into an equatorial plate. Within the nucleus the bulk of the solids 
collected at the side toward the anode. The nucleolus usually 
migrated toward the anode. No influence was exerted on division 
figures, spindles and chromosomes showing no sign of orientation 
or displacement whatever. 
A careful review of the literature of this type of work reveals 
that current intensity was seldom measured accurately, and in 
most cases even when measured the results are not always repro- 
ducible because the organisms or organs studied were usually 
mounted in water, which acts as a partial conductor of current 
(conductivity varying with quantity of liquid used, electrolytes 
present, temperature, etc.), and in such experiments it is impossible 
to determine what part of the current flowed arlene the plant 
and what part through the water. 
EFFECT OF CURRENT ON PARTICLES SUSPENDED IN LIQUIDS 
The fact has long been known that finely divided particles 
suspended in water or other poorly conducting media will migrate, 
if the electric current is passed through the liquid, toward one or 
the other of the electrodes. Suspensions in water of starch, par- 
ticles of paper, earth, asbestos, finely divided gold and copper all 
